- majtitle_gfx_ctrl_w is unknown, it seems to be used to disable rowscroll, and maybe other things.

- Maybe there is a layer enable register, e.g. nspirit shows (for an instant) incomplete screens with bad colors when you start a game.

- A lot of unknown I/O writes from the sound CPU in Pound for Pound.

- The sprite chip triggers IRQ1 when it has finished copying the sprite RAM to its private buffer. This isn't implemented (all games have an empty IRQ1 handler). The cpu board also has support for IRQ3 and IRQ4, coming from the external connectors, but I don't think they are used by any game.

NOTES:

- Driver by Nicola Salmoria and protection information by Nao.

- The driver supported IREM M72, M73, M81, M82, M84 and M85 board games. X Multiply (M72) has different addressing PALs, so different memory map. rtype2j has M84 written on the board, but it's the same hardware as rtype2. For Gallop (IREM M73) there is also a M84 version.

- Sample playback: In the later IREM games, the sound CPU can program the start offset of the PCM samples, but it seems the earlier games have them hardcoded somewhere (maybe a PROM?). MAME uses tables with the start offset precomputed. They could be built automatically for the most part (00 marks the end of a sample), but some games have holes in the numbering so we would have to do some alterations anyway. The table for Gallop is most likely wrong, and it doesn't play anything anyway, because the NMI handler of the sound CPU consists of just RETN - so it must be using different hardware.

Bugs:

- dbreed, rtype2: Play samples too slow, i have recorded examples from my Dragon Breed(m81) and R-Type 2(M84) for comparison. But the music is played at correct speed? Stefan Lindberg (ID 00202)

WIP:

- 0.148: Robbbert fixed cocktail mode in airduel and imgfight (background pushed 1/2 off right side when flipped).

- 0.126u5: Fabio Priuli changed a lot of input related things in IREM M10->M107 boards. First of all, moved input definitions from drivers\m92.h to include\iremipt.h and removed completely drivers\m92.h (which only contained those definitions). Added more common inputs to iremipt.h and started to use that file in m62->m107 instead of local #defines. Finally, added DIP locations to all the games in m62->m107 which were missing and it implemented coinage mode 2 through dipconditions in the drivers which didn't support it.

- 0.36RC1: Struct GfxLayout can now be parametric on the size of the memory region it refers to. This way the same gfx definition can be used for games with the same layout but different number of tiles. See M72 and DEC0 driver for usage examples [Nicola Salmoria].

- 0.36b6: Added m72.c driver vidhrdw\m72.c and sndhrdw\m72.c/h. Most of the non working games are protected, at least some of them have a 8751 MCU. bchopper, nspirit, imgfight, loht are patched to get into service mode. Major Title is supposed to disable rowscroll after a shot, but Nicola haven't found how. Sprite/tile priorities are not completely understood. Sample playback works only in R-Type II and Hammerin' Harry. The other games have similar hardware but Nicola don't understand how the sound CPU is supposed to get the command to play a sample.

- 28th September 1999: Nicola sent in an M72 update with priorities fixed and Major Title added.

- 25th September 1999: Nicola added Gallop to the M72 driver, but the rest of the M72 games need their i8751 MCU emulated before they work.